Many concrete or similar structural components conventionally are relatively thick and heavy, compared to their weight bearing capacity. The formation of voids within concrete can improve the economics, performance, and versatility of the concrete and its implementation.
Prestressed, prefabricated concrete elements with extended cross sections and internal hollow cylindrical cavities have been used to reduce the weight “problems”, but they typically only span in a “single” direction. In other words, they are typically relatively long and narrow concrete beams with one or more web elements extending significantly below the concrete “deck.” Alternative approaches have included placing lightweight balls within the concrete as it is poured (for example, see DE 2,116,479) or similarly positioning hollow spheres within a mesh assembly in the concrete (for example, see U.S. Pat. No. 5,396,747, issued to Breuning in 1995).
A system using embedded blow-molded plastic balls is described at the website of BubbleDeck North America Ltd. BubbleDeck currently produces a pre-fabricated solid concrete slab structure having plastic balls embedded in concrete, to reduce the slab's weight. According to BubbleDeck, the pre-fabricated concrete slab can reduce construction material weight by up to fifty percent (50%). The BubbleDeck plastic balls are hollow, spherical shapes (similar to ping pong balls), and are of a solid fixed single piece construction. That single piece hollow body construction apparently has a generally uniform wall thickness sufficient to withstand the stress imposed by the surrounding concrete material, but that solid fixed single piece construction limits at least the shipping and handling characteristics of the inserts (balls) prior to use, and can also affect the stress handling capacity of the plastic balls.
Thus, the weight advantages of systems such as the BubbleDeck balls are compromised by certain disadvantages inherent in their design. Among other things, because they are blow-molded spheres, they are cannot be efficiently stored or transported prior to their use on a jobsite.